Cutting tools and roughened articles using surface roughening methods

ABSTRACT

The disclosure relates to surface roughening methods in which a cutting tool having a radial cutting blade with first and second cutting edges is fed along a longitudinal axis of an article while rotating the cutting tool about the axis. The first cutting edge forms a first machined pattern of peaks and valleys on a surface of the article, and the second cutting edge removes at least a portion of the peaks to form roughened fracture surfaces in a second machined pattern defining an arrangement of grooves, corresponding to the valleys, separated by lands, corresponding to the roughened fracture surfaces. The disclosure also provides cutting tools useful in practicing the surface roughening methods. The disclosure further describes cylindrical articles having interior or exterior surfaces roughened using the methods. The methods, cutting tools and articles have applications including fabrication of cylinder blocks for internal combustion engines.

This application is a National Stage filing under 35 USC 371 ofInternational Application No. PCT/IB2005/003694, filed Dec. 7, 2005,which claims priority to Japanese Patent Application No. 2004-358712,filed Dec. 10, 2004, the entire contents of each of which isincorporated herein by reference.

TECHNICAL FIELD

The invention relates to methods of surface roughening and cutting toolsuseful in surface roughening, as well as articles having roughenedsurfaces, particularly articles useful in manufacturing internalcombustion engines for motor vehicle applications.

BACKGROUND

Internal combustion engines are increasingly fabricated usinglightweight metals such as aluminum to decrease weight and achievegreater fuel efficiency. In particular, aluminum cylinder blocks haverecently been fabricated with the internal surfaces of the cylinderbores spray coated with a material which acts to lubricate the cylinderbore and which aids the disposal of the engine's exhaust gases, forexample, by catalyzing chemical reactions associated with the combustionprocess.

When the inner surface of a cylinder bore of a liner-less aluminumcylinder block is spray-coated, it is generally necessary to roughen theinner surface of the cylinder bore beforehand to enhance the adhesion ofthe spray coating. Surface roughening may be achieved, for example,using bead blasting, high pressure water jet blasting, or mechanicalmachining methods. However, these methods may not lead to a uniformlyroughened surface, which can lead to adhesion failure of the coating tothe cylinder wall. In addition, conventional machining methods can betime intensive and expensive, often requiring multiple pass machiningsteps to produce a cylinder bore surface having sufficient roughness toadhere the thermally sprayed coating.

Thus, a more reproducible and cost effective surface roughening methodhas been sought. The art continually searches for new methods of surfaceroughening, particularly roughening of cylindrical metal surfaces usefulin fabricating internal combustion engines.

SUMMARY

In general, the disclosure relates to methods of surface roughening,cutting tools useful in practicing the surface roughening methods, andarticles having surfaces roughened using the methods. More particularly,the disclosure relates to mechanical surface roughening methods usefulfor metal surfaces, more specifically, cylindrical metal surfaces. Thesurface roughening methods, cutting tools and articles, may be useful inmanufacturing internal combustion engines for motor vehicleapplications.

In one embodiment, the method includes forming a pattern of peaks andvalleys on a surface of an article in a longitudinal axial directionwith a leading edge of a rotary cutting head having the leading edge anda trailing edge, applying a stress to the peaks with the trailing edgeof the cutting head, and fracturing the peaks to create a fracturesurface defining lands separating the valleys defining grooves. Incertain embodiments, each groove is symmetrical. In some embodiments,each groove defines a v-shape.

In additional embodiments, the method includes applying a coating to theroughened surface. In certain embodiments, the coating is applied usingat least one of chemical vapor deposition, plasma deposition, thermalspray coating, and fluid spray coating. The coating may include anabrasion resistant material. In some embodiments, the coating includes aceramic material or a metal.

In one exemplary embodiment, the method includes feeding a cutting toolcomprising a cutting head further comprising a radial cutting blade withfirst and second cutting edges along a longitudinal axis of an articlewhile rotating the cutting head about the axis. The first cutting edgeforms a first machined pattern of peaks and valleys on a surface of thearticle, and the second cutting edge removes at least a portion of thepeaks to form roughened fracture surfaces in a second machined patterndefining an arrangement of grooves, corresponding to the valleys,separated by the roughened fracture surfaces.

In another embodiment, a cutting tool comprises a rotary cutting headincluding at least one cutting blade extending radially outward from acutting head. The cutting blade has a body, a first planar surfacedefining a first cutting edge shaped to cut a first pattern of peaks andvalleys into a surface, and a second planar surface defining a fracturesurface formation blade shaped to fracture the peaks and thereby createlands separating the valleys forming grooves in a second pattern. Thecutting head may include at least one of a metal, a ceramic, or diamond.

In some embodiments, the cutting edge applies stress to a cross-sectionof each peak in an axial direction along a longitudinal axis of asurface at a starting location, and the fracture surface formation bladefractures each peak beginning at the starting location. In certainembodiments, the fracture surface formation blade fractures the entirecross section of each peak in the axial direction by applying the stressto the entire peak in a non-axial direction. In additional embodiments,the fracture surface formation blade includes an irregularly shaped parthaving a plurality of fracture surface formation blade projections anddepressions adapted to form an irregularly shaped fracture surfacedefining a land including a plurality of fracture surface projectionsand depressions formed by fracturing the entire cross section of eachpeak. In exemplary embodiments, the lands are additionally roughened bythe trailing edge of the cutting head.

In another embodiment, a surface roughening system comprises a means forroughening a surface further comprising a first cutting edge means forcutting a first pattern of peaks and valleys into the surface. The meansfor roughening further comprises a second cutting edge means forfracturing the peaks, a means for moving the means for roughening in anaxial direction relative to a longitudinal axis of the surface, and ameans for rotating the means for roughening in a radial directionrelative to the surface. According to certain embodiments of thissurface roughening system, rotating the means for roughening whilefeeding the means for roughening relative to the surface creates aroughened surface comprising a second pattern, wherein the secondpattern includes a plurality of lands created by fracturing the peaks,each land positioned adjacent to a groove corresponding to a valley inthe first pattern.

In yet another embodiment, a cylindrical body comprises a machineroughened surface including a substantially helical pattern of groovesseparated by substantially uniform roughened surface regions defininglands. In some embodiments, the cross section of the grooves issubstantially symmetrical and has a v-shape. In certain embodiments, theroughened surface is an interior surface of the cylindrical body. Insome embodiments, the cylindrical body may be formed from a nonferrousmetal. In additional embodiments, a coating is applied to the surfaceoverlaying the lands and grooves.

In certain embodiments, the cylindrical body is a cylinder block for aninternal combustion engine. In exemplary embodiments, the articleincludes at least one cylinder liner positioned in the cylinder bore ofthe engine. The cylinder liner may include an outer peripheral surfaceroughened by forming thereon the pattern of lands and grooves, beforecasting the cylinder liner into a cylinder bore of an internalcombustion engine.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view of a cylinder block showing a surfaceroughening method.

FIG. 2 is a front view of an exemplary cutting tool useful in practicingthe surface roughening method of FIG. 1.

FIG. 3 is a side view of the cutting tool of FIG. 2.

FIG. 4 is a bottom view of the cutting tool of FIG. 2.

FIG. 5 is an enlarged perspective view of the cutting head of theexemplary cutting tool of FIG. 2.

FIG. 5A is an enlarged perspective view of the cutting edges on thecutting head of the exemplary cutting tool of FIG. 2.

FIG. 6 is an overhead view in perspective of the cutting head of FIG. 5.

FIG. 7 is an enlarged cross-sectional view showing a state of cuttingwith a cutting blade that is part of the cutting head of FIG. 5.

FIG. 8 is a front view of a cutting tool showing another exemplaryembodiment of a cutting head.

FIG. 9 is a cross-sectional view showing an enlargement of a part D inFIG. 8.

FIG. 10 is an enlarged cross-sectional view showing the state of cuttingwith a cutting blade that is part of the cutting head of FIG. 8.

FIG. 11 is a cross-sectional view showing the state of cutting with acutting head that includes an irregularly shaped fracture surfaceformation blade that additionally roughens a fracture surface.

FIG. 12 is a block diagram showing an outline of exemplary thermalspraying equipment useful in forming a thermal spray coating on acylinder bore inner surface that is roughened.

FIG. 13 is a cross-sectional view of an exemplary surface roughenedcylinder block (e.g. made of an aluminum alloy) for an internalcombustion engine in which a cylinder liner (e.g. made of cast iron) isintegrally molded.

FIG. 14A is an overheard view of the cylinder liner in FIG. 13.

FIG. 14B is a perspective view of FIG. 14A showing the roughenedexterior peripheral surface of the cylinder liner of FIG. 13.

FIG. 15 is an exploded perspective view of exemplary casting molds usedto cast and form a cylinder block for an internal combustion engine asshown in FIG. 13.

DETAILED DESCRIPTION

The present invention is generally related to a surface rougheningmethod in which a cutting tool is moved along a longitudinal axis of abody. As the cutting tool rotates about the longitudinal axis of thebody, a first cutting edge extending radially outward a first distancefrom a cutting head of the cutting tool moves relative to the body andcuts on a surface of the body a first machined pattern of peaks andvalleys. A second cutting edge extending radially outward a seconddistance from the cutting head of the cutting tool applies stress on thepeaks in the first pattern, which fractures the peaks to createfractured surfaces and form a second machined pattern in the on thesurface of the body. In the second machined pattern the fracturedsurfaces are lands separated by grooves, which correspond to the valleysremaining from the first machined pattern. By fracturing the peaks usingthe second cutting edge of the cutting tool, the lands of the secondmachined pattern are more uniform and symmetrical compared to machiningtechniques in which the fracture surface is formed by cutting chipsgenerated as the machining proceeds.

The surface roughening method according to some embodiments of thepresent invention may thus lead to more uniformly shaped surfaceroughness patterns, which increases the adhesion strength and uniformityof a thermal spray coating applied to the roughened surface. Theroughened surface may be used in, for example, an internal surface of acylinder bore of an internal combustion engine. In additionalembodiments, the adhesion strength between two articles may also beincreased using the surface roughening method to roughen an externalperipheral surface of, for example, a cylinder liner that is to beinserted as a sleeve into a cast cylinder block.

Various exemplary embodiments of the present invention will now bedescribed with reference to the drawings. By specifying particular stepsin the present disclosure, it is not meant to limit the invention toperforming those steps in a particular order unless an order isspecified. Similarly, listing particular steps in a particular order isnot intended to preclude intermediate steps or additional steps, as longas the enumerated steps appear in the order as specified. Certainmaterials and articles suitable for practicing the present invention aredisclosed; however, additional equivalent materials and articles may besubstituted in practicing the invention, as known to one skilled in theart. The detailed description of the present invention is not intendedto describe every embodiment or each implementation of the presentinvention. Other embodiments and their equivalents are within the scopeof the present invention.

In the particular examples described below and in FIG. 1, the article tobe surface roughened is a cylinder bore 3 of a cylinder block 1. Thebore 3 has a cylindrical body, and a cylinder bore inner surface 5 thatis to be roughened. However, the surface to be roughened need not be aninner surface, but may be an outer surface. The article to be roughenedusing the surface roughening methods described herein is not limited toa cylinder bore part, but may, for example, be a pipe, a cylindricalbearing surface (e.g. a boss within a tie rod or other bearing surface),a transmission, and the like. In addition, the article need not have acylindrical shape.

The article may be formed using any number of methods; however,die-casting is a presently preferred method. The article may generallybe formed from a metal, for example, a nonferrous metal alloy such as analuminum alloy (e.g. ADC 12 manufactured by Nissan Motors Company,Tokyo, Japan). However, other machinable materials (e.g. rigid plasticsand the like) may be used in practicing the invention according to someembodiments.

FIG. 1 is a cross-sectional view of a cylinder block 1 of an engineshowing a surface roughening method, cutting tool and article accordingto various embodiments of the present invention. Once the cylinder boreinner surface 5 is roughened by means of the method described below, acoating material may be applied to the roughened cylinder bore innersurface 5 to form a coating. In some embodiments, the coating is appliedusing at least one of chemical vapor deposition, plasma deposition,thermal spray coating, and fluid spray coating. Preferably, the coatingis applied using thermal spray coating. The coating may include anabrasion resistant material. In some embodiments, the coating includes aceramic material or a metal. Preferably, the thermal spray coatingmaterial includes a ferrous metal.

As shown in FIG. 2, a cutting tool including a boring bar 9 terminatingat a radial cutting head 7 may be used to roughen the surface of thecylinder bore inner surface 5. FIG. 3 is a side view of the cutting toolof FIG. 2, and FIG. 4 is a bottom view of the cutting tool of FIG. 2. Onthe boring bar 9, a notch 13 that is used to form a concave surface isformed on the side of the tip of the lower part of a tool body 11 inFIG. 2, and the cutting head 7 is fixed by fastening with a bolt 15 atthe end of the tool body 11 that protrudes from the notch 13. FIG. 5 isan enlarged perspective view of the cutting head 7 shown in the FIG. 2,and FIG. 6 is an overhead view of FIG. 5.

In one exemplary method of surface roughening, the cutting head 7 movesalong the longitudinal axis A of the cylinder 3 (FIG. 1). The tool body11 rotates about the longitudinal axis B (FIG. 1), and a single cuttingblade 7 a protrudes outward from a side face 11 a of the tool body 11 tocut the surface 5 into a substantially helical thread-like pattern toroughen the surface. However, the surface roughening method may also beperformed by holding the boring bar 9 may in a fixed state and movingthe cylinder block 1 axially and rotationally.

As shown in FIGS. 5, 5A and 6, this exemplary cutting head 7 includesthree cutting blades 7 a extending radially outward from the body 8 ofthe cutting head at even angular intervals. In certain embodiments, eachof the three cutting blades 7 a can be removed when worn from cutting,and by attaching them on the tool body 11 again while rotating thecutting head body 8 120 degrees from the state in FIG. 4, another freshcutting blade 7 a can be used. It should be emphasized that the cuttinghead configuration shown in FIGS. 5, 5A and 6 is only exemplary, andmany different cutting tool shapes may be used, as long as a firstcutting edge of the cutting blade makes a pattern of peaks and a secondcutting edge fractures the peaks to form fracture surfaces.

Referring to FIGS. 5, 5A and 6, each cutting blade 7 a includes a firstplanar region 7 b oriented at an obtuse angle δ below a plane formed bythe body 8 of the cutting head 7. The first planar region 8 b extendsradially outward a first distance d₁ from a center 8 b of the body 8 andintersects with a first rake face 7 d to form a first cutting edge 7 g.The angle σ between the first planar surface 7 b and the first rake face7 d is selected to form a pattern of peaks and valleys in the surface tobe cut. The angle σ is typically selected such that each machined valleyin the surface 5 is symmetrical, and in a preferred embodiment eachvalley has a cross sectional v-shape. The first planar region 7 bextends from the first rake face 7 d at a leading edge of the cuttingblade 7 a, which is substantially normal to the planar region 7 b, to asecond rake face 7 e at a trailing edge of the cutting blade 7 a, whichis also substantially normal to the planar region 7 b. A second planarregion 7 c is formed at an acute angle θ above the first planar region 7b. The second planar region 7 c extends radially outward a seconddistance d₂ from the center 8 b of the body 8 and intersects with thefirst rake face 7 d to form a second cutting edge 7 h. The second planarregion 7 c also extends from the first leading edge rake face 7 d to thesecond trailing edge rake face 7 e. The second planar region 7 c issubstantially normal to an end face 7 f, which may optionally include asurface pattern.

In operation, the first cutting edge 7 g cuts into the surface 5 of thecylindrical body a first machined pattern of peaks and valleys, and thefirst machined pattern will typically be a substantially helicalthread-like pattern. The first cutting edge 7 g preferably has an angleσ selected such that each machined valley in the surface 5 issymmetrical, and in a preferred embodiment each valley has a v-shapewhen viewed in cross section. The second cutting edge 7 h then appliesstress to the peaks of the first substantially helical pattern, whichfractures the peaks and forms a second machined pattern in the surface5. The second machined pattern is also typically a substantially helicalthread-like pattern. In the second machined pattern the fractured peakscreate fracture surfaces separated by grooves, which are the valleysremaining from the first machined pattern.

The cutting head 7 may be fabricated from any number of materials, butgenerally includes at least one of a metal, a ceramic material, ordiamond. The cutting blades 7 a generally include at least one metalselected from titanium, tungsten, cobalt, nickel, iron, or aluminum. Thecutting edge 7 a and in particular, the fracture surface formationsecond cutting edge 7 h, may include at least one ceramic materialselected from one or more of silicon nitride, silicon carbide, aluminumoxide, silicon dioxide, or titanium nitride. Preferably, the cuttingblades 7 a are harder than the surface of the material to be roughened.

In some embodiments, the disclosure provides a surface rougheningsystem, including a means for roughening a surface (e.g. cutting head7), further including a first cutting edge means (e.g. first cuttingedge 7 g) for cutting a pattern of peaks and valleys into the surface toform the first substantially helical pattern, and a second cutting edgemeans (e.g. fracture surface second cutting edge 7 h) for fracturing thepeaks to form the second substantially helical pattern includingroughened lands interspersed with grooves; a means for feeding (notshown in FIG. 1); and a means for rotating (not shown in FIG. 1).

As shown in FIG. 7, which shows cutting using the cutting blade 7 a inwhich the parts shown in FIGS. 5, 5A and 6 are enlarged, the firstplanar region 7 c with the second cutting edge 7 h applies stress on apeak 17 remaining from the first machined pattern formed by the firstcutting edge 7 g on the cylinder bore inner surface 5. The secondcutting edge 7 h removes a portion of the peak 17 and forms a fracturesurface 19. A cutting chip 21 is generated by the cut with the cuttingblade 7 a, and the cutting head 7 is assumed to move out of the plane ofthe paper in FIG. 7 and vertically upward toward the viewer.

In the perspective of FIG. 7, the projecting part 7 c and second cuttingedge 7 h of the cutting blade 7 a apply stress beneath the peak 17 andthe cutting blade 7 a moved vertically upward toward the viewer and outof the paper to fracture the peak 17 and form a fracture surface 19.Using the above described cutting tool 7 a make the peak 17 relativelyeasy to fracture in a uniform and consistent way, and the shape of thefracture surface 19 is more uniform and symmetrical compared toconventional processes in which the fracture surface is randomly formedby cutting chips produced by the first cutting edge of the cuttingblade. In addition, since the peak 17 is easily fractured using theprojecting part 7 c, the cutting stress applied on the cutting blade 7 ais reduced, which would be expected to extend the life of the cuttinghead 7. Preferably, as shown in FIG. 7, the entire cross section of eachpeak in the axial direction is fractured by applying the stress to eachpeak in a non-axial direction.

Since the shape of the fracture surface 19 is more uniform andsymmetrical as described above, the coating applied to the surface 5adheres more strongly and more uniformly, which enhances the durabilityof the coating.

FIG. 8 is a perspective view of a cutting head 70 corresponding to FIGS.5, 5A and 6 showing another embodiment of the present invention. Thisexemplary cutting head 70 again includes three cutting blades 70 a eachextending radially outward at even angular intervals.

Each cutting head 70 a includes a first planar region 70 b oriented atan obtuse angle δ below a plane formed by the body 80 of the cuttinghead. The first planar region 80 b extends radially outward a firstdistance d₁ from a center 80 b of the body 80 and intersects with afirst rake face 70 d to form a first cutting edge 70 g. The first planarregion 70 b extends from the first rake face 70 d at a leading edge ofthe cutting blade 70 a, which is substantially normal to the planarregion 70 b, to a second rake face 70 e at a trailing edge of thecutting blade 70 a, which is also substantially normal to the firstplanar region 70 b. A second planar region 70 c is formed at an acuteangle θ above the first planar region 70 b. The second planar region 70c extends radially outward a second distance d₂ from the center 80 b ofthe body 80. A second cutting surface or rake face 70 h, substantiallynormal to the second planar region 70 c, is formed at an intersectionwith an end face 70 f, which is also substantially normal to the secondplanar region 70 c. The distance x₂ between the second cutting surfaceor rake face at the leading edge of the second planar region 70 c and arake face 70 i at the trailing edge of the second planar region 70 c isless than the distance x₁ between the first rake face 70 d at theleading edge of the first planar region 70 b and the second rake face 70e at the trailing edge of the first planar region 70 b.

FIG. 9 shows view D corresponding to the arrow in FIG. 8, wherein, arake face 70 d of the cutting blade 70 a is oriented at an angled α withrespect to a direction opposite to the rotational direction B of thecutting head 7 in FIG. 4 and with respect to a line L normal to thecylinder bore inner surface 5. The orientation of the rake face 7 d inFIG. 5A may also be selected to have the same orientation as the rakeface 70 d in FIG. 9. At the same time, a rake face 70 h adjacent thesecond planar surface part 70 c is oriented at an angle β in therotational direction B with respect to a line M drawn orthogonal to thesurface 5 to be roughened.

FIG. 10 illustrates a cutting procedure using the cutting head of FIG.8. The first cutting edge 70 g cuts into the surface 5 of thecylindrical body a first machined pattern of peaks and valleys, which ispreferably a substantially helical thread-like pattern. The firstcutting edge 70 g is typically shaped at an angle σ with respect to thefirst rake face 70 d such that each machined valley in the surface 5 issymmetrical, and in a preferred embodiment each valley has a v-shapewhen viewed in cross section. The second cutting edge 70 h then appliesstress to the peaks of the first machined pattern, which fractures thepeaks and forms a second machined pattern in the surface 5, which alsosubstantially helical. In the second machined pattern the fracturedpeaks form a patterns of roughened lands separated by grooves, which arethe valleys remaining from the first machined pattern.

The second cutting edge 70 h preferably removes the entire crossdirection of the peak 17 (vertical direction in FIG. 10 and up out ofthe paper toward the viewer) to form a fracture surface 19 that isalmost the same as that shown in FIG. 7. The end face 70 f that islocated at the tip of the second planar region 70 c then contacts thefracture surface 19 after the peak 17 is removed. Since the rake surface70 h of the projecting part 70 c is oriented at an angle β in therotational direction B with respect to a line M normal to the surface 5,while the rake surface 70 d is oriented at an angle α in the directionopposite the rotational direction B with respect to ah line L normal tothe surface 5, the removal of the peak 17 may be more reliably performedcompared to a tool design in which the rake surface 70 h is oriented inthe same direction as the rake surface 70 d.

In certain presently preferred embodiments, the trailing edge of thecutting head may also roughen the surface of each land after the peak isfractured and removed, which increases the surface area of the land andmay enhance adhesion of the coating to the land. FIG. 11 is across-sectional view corresponding to FIG. 10 showing an example of acutting head 70 useful in practicing this presently preferredembodiment. In this example, an irregularly shaped part with projectionsand recessions which makes the irregularly shaped fracture surface 19with projections and recessions is provided on an end face 70 fs in thesecond planar surface 70 c of the cutting head 70, which contacts thefracture surface 19 after the peak 17 is removed by the second cuttingsurface 70 h. The roughened surface 70 fs creates a finer surfacetexture on the fracture surfaces 19, which enhances the surface area andwould be expected to increase the adhesion of the coating.

FIG. 12 is a block diagram showing an outline of exemplary thermalspraying equipment useful in forming a roughened surface on a cylinderbore inner surface according to another embodiment of the presentinvention. FIG. 12 illustrates an schematic of the thermal sprayingequipment used to form a thermal spray coating after roughening thesurface on the cylinder bore inner surface 5 of the cylinder block 1.This exemplary thermal spraying equipment inserts a gas wire thermalspraying gun 31 into the center of a cylinder bore, and a fused ferrousmetallic material of a thermal spraying material is sprayed in the formof droplets 33 from a thermal spraying port 31 a to form a thermal spraycoating 32 on the cylinder bore inner surface 5.

The thermal spraying gun 31 may be fed a supply of melting wire 37 of aferrous metallic material as the material for thermal spraying from amelting wire feeding machine 35, and further may receive a supply of afuel gas and oxygen from a fuel gas cylinder 39 which stores fuel suchas acetylene, propane, ethylene, and the like; and from an oxygencylinder 41 which stores oxygen and delivers oxygen gas, through piping43 and 45 respectively. The melting wire 37 may be fed to the thermalspraying gun 31 from the upper end to the lower side of a melting wirefeed hole 47 that vertically penetrates the central part of the gun. Inaddition, the fuel and oxygen may be supplied to a gas guide channel 51that is formed by vertically penetrating a cylindrical part 49 locatedon the outside of the melting wire feed hole 47. This mixed gas supplyof fuel and oxygen may flow out from a lower end opening 51 a of the gasguide channel 51 in FIG. 12 and when ignited, forms a combustion flame53.

An atomized-air channel 55 may be provided on the outer circumference ofthe cylindrical body 49, and an accelerated-air channel 61 formedbetween a cylindrical bulkhead 57 and a cylindrical external wall 59 isprovided outside of the atomized-air channel. Atomized-air flowingthrough the atomized-air channel 55, may be pre-heated by the combustionflame 53, and fed forward (downward in FIG. 12) in order to allow theperimeter part to cool. Atomized-air may also be fed forward to thefused melting wire 37. At or about the same time, accelerated-airflowing through the accelerated-air channel 61 is also fed forward, andfeeds the melted melting wire 37 to the cylinder bore inner surface 3 asdroplets 33 so that it intersects with the feed direction to form thesprayed coating 32 on the cylinder bore inner surface 5.

Atomized-air may be supplied to the atomized-air channel 55 from anatomized-air supply source 67 through an air supply pipe 71 with apressure regulator 69. At or about the same time, accelerated-air issupplied to the accelerated-air channel 61 from an accelerated-airsupply source 73 through an air supply pipe 79 with a pressure regulator75 and a micromist filter 77. The bulkhead 57 between the atomized-airchannel 55 and the accelerated-air channel 61 includes of a rotarycylinder part 83 which can be rotated through a bearing 81 of theexternal wall 59 at the tip of the lower side in FIG. 12. A rotary wing85 that is located in the accelerated-air channel 61 is provided on theupper outer circumference of this rotary cylinder part 83. Whenaccelerated-air flowing through the accelerated-air channel 61 works onthe rotary wing 85, the rotary cylinder part 83 rotates.

A tip part 87 that rotates integrally with the rotary cylinder part 83may be fixed on the tip (lower end) 83 a of the rotary cylinder part 83.A projecting part 91 with a spout channel 89 that communicates with theaccelerated-air channel 61 through the bearing 81 is provided on onepart of the peripheral edge of the tip part 87, and the thermal sprayingport 31 a which spouts out droplets 33 is provided at the tip of thespout channel 89. By rotating the tip part 87 with the thermal sprayingport 31 a integrally with the rotary cylinder part 83, while moving thethermal spraying gun 31 in the axial direction of the cylinder bore, asprayed coating 32 is formed on almost the entire area of the cylinderbore inner surface 5.

Although in each of the embodiments explained above, surface rougheningis performed at the internal surface of cylindrical bodies such as withthe cylinder bore inner surface 5, another embodiment explained belowillustrates increasing the bonding strength of a cylinder liner 103 witha cylinder block 101 by roughening the outer peripheral surface 103 a ofthe cylinder liner 103, that is the outer surface of a cylindrical body,by means of a similar method to the cylinder bore inner surface 5 ineach of the embodiments described above. This embodiment may beparticularly useful when the cylinder liner 103 is made of, for example,cast iron, and the cylindrical body is cast into a cylinder block 101that is made of, for example, an aluminum alloy, as shown in FIG. 13.

FIG. 14A is a top view of the cylinder liner 103 in FIG. 13, and FIG.14B is a plane view of FIG. 14A showing the roughened exteriorperipheral surface 103 a of the cylinder liner 103 of FIG. 13. The outerperipheral surface 103 a of the cylinder liner 103 is cut into a firstsubstantially helical pattern of peaks and valleys using the cuttingblade 7 a (70 a) of the boring bar 9 with the cutting head 7 or 70 asshown in FIG. 2. The peaks 17 of this first substantially helicalpattern are fractured by the leading edge 7 h (70 h) of the projectionformed by the second planar surface 7 c (projecting part 70 c) to form apattern of grooves interspersed with fracture surfaces 19 as shown inFIG. 7. In this manner, a cylinder liner 103 can be obtained in whichthe outer peripheral surface 103 a is roughened as shown in FIG. 14 (a).

In another embodiment shown in FIG. 15, the cylindrical cylinder liner103 with the roughened outer peripheral surface 103 a may be cast tomold integrally when the cylinder block 101 is cast with a casting mold.The casting mold includes of a bottom die 105, an upper die 107, rightand left side die 109 and 111, front and rear die 113 and 115, and anejector plate 117 installed in the upper part of the upper die 107. Abore core 107 a for forming a cylinder bore 101 a of the cylinder block101 is provided at the side opposite to the bottom die 105 of the upperdie 107, and the cylinder block 101 is cast and formed in a state suchthat the cylinder liner 103 is kept as shown in FIG. 14 on this borecore 107 a.

As shown in FIG. 1 and FIG. 13, the cylinder bore part 3 of cylinderblock 101 in which the cylinder liner 103 is cast, can also be surfaceroughened according to various previously described embodiments of thepresently disclosed invention. In addition, since the outer peripheralsurface 103 a of the cylinder liner 103 may be roughened using the sameor a similar method to that used for the cylinder bore inner surface 5at about the same time, the joining strength of the cylinder block 101for the cylinder liner 103 can be increased and a cylinder block 101 ofhigh quality can be obtained.

Various embodiments of the invention have been described. These andother embodiments are within the scope of the following claims.

1. A surface roughening method, comprising: moving a cutting tool havinga cutting head along a longitudinal axis of an article, wherein thecutting head comprises a radial cutting blade having a first cuttingedge and a second cutting edge; and rotating the cutting head about thelongitudinal axis of the article such that the first cutting edge of thecutting blade forms a first machined pattern of peaks and valleys on asurface of the article, and such that the second cutting edge of thecutting blade removes at least a portion of the peaks in the firstmachined pattern to form uniform roughened fracture surfaces in a secondmachined pattern on the surface of the article, and wherein the secondmachined pattern comprises an arrangement of grooves corresponding tothe valleys in the first pattern and separated by lands corresponding tothe uniform roughened fracture surfaces.
 2. The method of claim 1,wherein an entire cross section of each peak in the first pattern isfractured.
 3. The method of claim 1, wherein each of the grooves in thesecond machined pattern is symmetrical.
 4. The method of claim 1,wherein each of the grooves in the second machined pattern defines av-shape.
 5. The method of claim 1, wherein a trailing edge of thecutting head roughens the surface of each land.
 6. The method of claim1, wherein the article defines a cylindrical body.
 7. The method ofclaim 6, wherein the first cutting edge cuts an interior surface of thecylindrical body into the first machined pattern comprising a firstsubstantially helical pattern defined by the alternating peaks andvalleys, and wherein the second cutting edge creates the uniformroughened fracture surfaces on the interior surface by applying stresson the peaks to fracture at least a portion of the peaks to form thesecond machined pattern comprising a second substantially helicalpattern defined by lands corresponding to the uniform roughened fracturesurfaces, separated by grooves corresponding to the valleys.
 8. Themethod of claim 1, wherein the article comprises a nonferrous metal. 9.The method of claim 1, further comprising applying a coating overlayingthe first and second machined patterns on the surface of the article.10. The method of claim 9, wherein the applying of the coating comprisesat least one of chemical vapor deposition, plasma deposition, thermalspray coating, or fluid spray coating.
 11. The method of claim 9,wherein the coating comprises an abrasion resistant material.
 12. Themethod of claim 9, wherein the coating comprises at least one of aceramic material or a ferrous metal.
 13. The method of claim 12, whereinthe ceramic material comprises one or more of silicon nitride, siliconcarbide, aluminum oxide, silicon dioxide, and titanium nitride.
 14. Themethod of claim 12, wherein the ferrous metal comprises one or more oftitanium, tungsten, cobalt, nickel, iron, and aluminum.